The present invention relates to protective helmets in general and, more particularly to an internal portion of the protective helmet, which is secured to the shell of the helmet.
Internal portions or structures for protective helmets usually comprise a plurality of belt bands or straps forming a spider, the ends of the belt straps being fastened to the shell of the helmet by means of fasteners. Conventional internal constructions of protective helmets include plug-in fasteners each being formed as an individual shackle which has been loosely connected at its one end to the cross-piece of the head bearing ring of the helmet and at its another end it has been provided with a plug stem of an enlarged cross-section. The plug stem, or foot has been inserted from below into a respective pocket formed in the helmet shell; this plug stem formed a force transmission portion from the helmet shell to the belt spider. Knobs have been provided on the front edge of the U-shaped plug stem, which knobs have been engaged in special stamp-outs formed in the belt straps.
In these known internal structures the fasteners have been made from relatively hard synthetic plastic material whereas the head bearing ring has been formed of soft plastics so that it can be easily adjusted to the head of a user.
The manufacture of these conventional internal structures is rather expensive because the head bearing ring itself as well as the plug locks or fasteners must be produced by at least four individual injection molding processes. The assembly of the individual components of the internal structure is also expensive because all the plug fasteners must be individually connected to the head bearing ring.
A further disadvantage of conventional internal structures is a fastening means utilized for securing the belt straps to the stems of the fasteners. In the case of high loads exerted on the belts a pulling force transmitted from the belt strap to the expanded stem of the fastener will push the latter from the pocket of the helmet shell. This will result in the transmission of the pulling force to the projections formed on the edge of the stem positioned in the pocket of the helmet shell.